This invention relates to flexible circuits. More particularly, it involves a cover layer for flexible circuits which provides increased flexibility therefor.
Flexible circuits have been gaining wide acceptance in industry as a commercially feasible method of making electrical interconnections in a variety of electronic applications. Flexible circuits are flat conductor cables having a plurality of spaced conductors bonded to a flexible insulating film or substrate. It has been generally accepted to provide a cover layer of another similar insulating film to cover or encapsulate the conductors to provide electrical insulation and protection from adverse environmental conditions. Heretofore, the cover layer has been merely an insulating film which has been bonded to the flexible circuits. This has been accomplished, for example, by using a single layer of an adhesive, such as an epoxy adhesive, to bond the insulating film of the cover layer to the conductors on the flexible circuit.
Although the use of flexible circuits has been ever increasing, its use has been limited in those applications which require that the flexible circuit be subjected to repeated bending at extremely acute angles. In such applications it has been found that the conductors of commercially available flexible circuits may snap and break under such conditions thereby resulting in a loss of electrical interconnection.